Fig. 3. IRAP-GFP is a good surrogate marker for GLUT4 vesicles in 3T3-L1 adipocytes. 3T3-L1 adipocytes were microinjected with a plasmid encoding IRAP-GFP. 16 hours later the cells were serum starved for 2 hours and then incubated in the absence (A,C) or presence (B) of transferrin-Alexa568 for 30 minutes. In C, the cells were incubated for 30 minutes in the absence or presence of insulin, as indicated. The cells were then fixed and stained with anti-GLUT4 antibodies (A, as indicated with GLUT4) as required. The images show the distribution of IRAP-GFP (visualised as GFP fluorescence), GLUT4 immunofluorescence or Tf-Alexa labelling, as indicated. A merged image is also provided.